The Dáil is the lower house of parliament in Ireland, the Seanad (Senate in English) is the upper house.

The index letters show the nature of the qualification of an Elector to vote.
S = Qualified to vote at election to Seanad Éireann
R = Residence qualification for the Dáil Election
BP = Business Premises qualification for the Dáil Election
O = Occupation qualification for the Local Government Election
HO = Husband's occupation qualification for the Local Government Election
The researcher has found no information on the jurors column.
Visit the Irish government's website www.environ.ie to learn more about the roles of the Dáil and Seanad